The Surprising Facts About Earth-Sheltered Living
Nov 26th, 2012 | By NathanF | Category: Energy, Miscellaneous, Top Headline | Print This Article
We have all heard the one about how if you dig a hole straight down into the earth, eventually you come out the other side of the planet in China. While theoretically this might be true, in the real world it would not be possible. If the tremendous pressures you would encounter didn’t do you in, the intense heat ultimately would, and at a certain depth all of your excavation and drilling equipment would melt (and you would too).
As we travel downward it gets hotter and hotter, and this precludes digging all the way to the center of the earth and beyond. But the earth’s capacity to produce and hold heat can be of great benefit to human beings. If instead of trying to dig to China we instead go just a few feet down, we will discover temperatures that are always moderate even on the most frigid winter days – and also on the hottest summer days, since the earth’s temperature at a depth of a few feet does not fluctuate more than slightly over the course of an entire calendar year. The planet’s natural warmth can be exploited as a source of energy (geothermal), but it can also be used to shelter living spaces and protect them from the elements all year round.
Yes, it is indeed possible to build homes that are partially or almost completely buried beneath the ground or the earth, and this type of residential construction has a lot to recommend it to those who are concerned with reducing costs and holding down their resource consumption.
Earth-Sheltered Living Options: A Summary And Assessment
While earth-sheltered housing is not common, it has been around for a while. During the energy crisis of the 1970s, people became increasingly interested in finding ways to reduce their consumption of fossil fuel, and energy-efficient forms of architectural design and construction began to draw a lot of attention. Underground living seemed to offer great promise, and many experiments were undertaken to explore potentially practical options for earth-sheltered homes that would be affordable and efficient.
These efforts met with mixed success, but the underground/earth-sheltered living movement never completely died out. In the years since the initial burst in interest introduced this unique and innovative style of building and living to the masses, much has been learned about what works and what doesn’t, and as a result people who are interested in constructing earth-sheltered dwellings now have some legitimate options to choose from.
The key principle that gives earth-sheltered homes their utility and viability is thermal mass. This scientific measuring standard rates the ability of materials to absorb and retain heat, and it turns out that the ground beneath our feet has a higher thermal mass than just about any other substance. The earth’s capacity to store heat and store a lot of it for a long period of time is quite impressive, and it is the ground’s thermal mass properties that explain the consistently warm-to-moderate temperatures we find when we move just a few feet down below the surface.
While some earth-sheltered homes are built completely beneath ground level, many are constructed using a technique known as berming. Earth-bermed homes are built largely above ground, but piles of soil are then pushed up against the walls – all the way to the top – to form a protective cocoon of earth and vegetation that will separate the outer shell of the home from the open air. Roof covers of soil and vegetation may or may not be included with earth-bermed homes, but most seem to prefer them since they do increase a house’s protection against atmospheric heat and cold.
There are three primary design styles for earth-sheltered homes: atrium, penetrational, and elevational. For those who would like to maximize their protection from the sun, the wind, the heat, and the cold, the atrium style is definitely the way to go. All of the rooms in such a residence are built completely beneath the surface of the earth, in a “town square” type of arrangement surrounding a central atrium space that functions as the home’s entrance from above ground. Each of the rooms of the home will face the atrium on the north, south, east, or west, with spacious windows and possibly glass doors to allow the natural light to filter in from above. A short flight of stairs down into the atrium is all that is necessary to reach the bottom of the home’s central space, as the underground rooms are generally placed no more than three feet beneath the earth’s surface, given that subterranean temperatures are steady beyond this point.
Because its open outdoor space and adjacent rooms and entrances are all below ground, the atrium style delivers the most privacy and the greatest amount of protection from the vagaries of nature (high winds, thunder storms, tornadoes, hurricanes, wildfires, etc.). However, because it is literally a hole in the ground, the atrium can easily fill with snow in a blizzard or rainwater in a tempest, which can cause flooding and drainage problems if some kind of system for diverting rain or melting snow has not been installed. Because the living areas are entirely beneath ground level, the rays of the sun are not able to enter at a low enough angle to provide ample amounts of natural light, and because the central outdoor space opens directly to the empty sky, the views enjoyed from inside the home are only as good as the effort that has gone into creating an attractive atrium space.
The elevational style, strictly speaking, is neither underground nor bermed, but is more of a combination of both. Elevational homes are built directly into hillsides or mountainsides, looking almost as if they have been inserted into the mouth of a cave, to enough depth to completely cover the side and back walls of the home. The front of the house is left open to the air, usually facing the south in order to harvest the natural heat and light provided by the daily sun. Roof covers are normally added to such a home to complement the berm-like sheltering effect of the hillside, and houses constructed in the elevational style have shallow rectangular shapes that feature bedrooms and living spaces arranged linearly in the foreground so the sun can provide heat and light to all the important rooms of the house. Elevational homes are the least expensive type of earth-sheltered structure to construct, and with their hillside locations they frequently offer grand panoramic views of surrounding natural vistas.
Penetrational homes are built above ground, but are designed to fully exploit the protective abilities of the earth. Each wall of a home constructed in the penetrational style is completely bermed, with only the spaces over doors and windows left open to facilitate easy entrance, good cross-ventilation, and the effective harvesting of natural light. Roof covers are the perfect finishing touches for such a home, which is so well protected from the elements that it might as well be completely under the ground, even though the entrance of light and air remains unobstructed. Variations on the penetrational approach are certainly possible; for example, the southern side could be left open as it is in an elevational home, while the rest of the house (save for the windows and the back door of course) would be fully bermed.
Problems And Issues
Inside the protective shell of the earth, temperatures generally remain between forty-five and sixty-five degrees Fahrenheit all year round, and it is this moderate range that allows underground homes to remain comfortable in all seasons. Because the surrounding temperatures are so mild, heating and cooling costs can be reduced from 50 to 70 percent in an earth-sheltered residence.
However, this will require the use of insulation, since unprotected walls will eventually reach thermal equilibrium with the surrounding earth unless steps are taken to ensure that heat produced or collected inside the home is not leached away through the walls. The value of the earth as a climate modifier does not come from its insulating properties, which are minimal, but rather from its capacity to soak up and hold warmth, allowing it to maintain a moderate temperature level and dramatically reduce the need for artificial heat or air conditioning in an earth-sheltered home. But thermal equilibrium must be avoided, since the temperature of the earth at a few feet below the surface is just a bit too cool for comfort. So insulation will need to be used on the outside of the walls in an underground or bermed home to make sure that livable temperatures can be maintained inside with less reliance on secondary heating sources – or no reliance on them at all in the summer time. To keep the insulation from touching the earth, a protective layer of board will have to be added, and the wood used must be thick and strong enough to withstand the pressure of the earth pressing against it without warping or breaking.
While insulation is important, before it can be added the outside areas of an underground or earth-bermed structure must be fully waterproofed. Thin sheets of plastic, rubber, or artificial rubber specially designed for home protection will need to be applied to the walls and the roof to make an earth-sheltered residence watertight, since the earth can easily pass on moisture to anything with which it comes in contact. With the insulation placed on top of the waterproofing, things are even more well protected, and a special type of drainage or filtration mat will need to be placed over the insulation on the roof in order to make sure that any moisture that comes from above can be easily channeled away. Underneath the poured concrete foundation of an earth-sheltered home, a layer of sand at least four inches deep (for the purposes of drainage) should be put in place, so that water cannot work its way into the home from below. A living roof made of soil and vegetation can provide even more protection from the elements, as much of the rain that falls from above or washes over the top of the home will be absorbed by the roots of the roof’s plant life before it can seep in deeper and cause trouble.
Choice of location for an earth-sheltered home will go a long way toward eliminating any potential moisture problems. Areas where run-off from rain or melting snow could be a factor should be avoided, as should locations that have low spots where water might collect. Most importantly, it is essential to always build above the water table, otherwise even the best waterproofing schemes will be tasked to the breaking point, and it may prove all but impossible to keep moisture from leaking through into the home.
The weight and pressure of the earth will obviously put an enormous strain on the walls and roof of an earth-sheltered home, which is why concrete makes an excellent choice for a building material. While poured concrete can work just fine for the foundation and the floor, concrete blocks stacked and coated with a thin layer of fiber-reinforced surface-bonding cement are the proper selection for the walls of an earth-sheltered home, which must bear up under lateral pressures that can be quite significant. Heavy timbers should be used to construct the roof, which must be able to handle the combined load of the earth above it and the snow that falls in winter.
Even though underground or earth-sheltered living is highly efficient, because it is unconventional and has some special requirements the costs of a home constructed in this style will generally run from 10 to 30 percent higher than the average aboveground structure. Ultimately, the return on investment provided by lower fuel costs will more than negate the extra upfront costs, but for some, the higher initial expenditures could be a deal breaker. Studies have shown that over the long haul, earth-sheltered building is most economical for those living in climates that have significant temperature extremes and low humidity, such as the Rocky Mountains and the northern Great Plains. Elevational homes are the cheapest to build, but they tend to pay for themselves quickly only in those locations where relatively long and cold winters are the norm.
One hidden problem that potential underground home owners must be aware of is the possible presence of radon, a colorless and odorless gas produced in the ground by uranium decay that can be life-threatening if it collects in sufficient concentrations. While it is not impossible to build an earth-sheltered structure in areas with elevated radon levels, steps will have to be taken to guarantee that all radon can be collected and vented from the home, which adds another layer of expense onto a project that already can cost a pretty penny.
The Undeniable Advantages Of Earth-Sheltered Living
To those hearing of it for the first time, underground living might sound more like exotic fantasy than practical reality, something we would put in the same category as flying cars or cities built beneath the surface of the sea. It all seems so impractical and fanciful somehow. But earth-sheltered living, far from being the stuff of science fiction, is actually a practical and cost-efficient option in many circumstances, as long as careful thought and effort are put into the design, site selection, and construction stages of the projects. A number of details must be taken care of to make sure an earth-sheltered home will be warm enough, sturdy enough, and dry enough to be livable and stand the test of time, and this precludes cutting corners or taking shortcuts that might compromise performance.
But once an earth-sheltered home is finished, what you will have on your hands is something very special indeed. Because it is protected from the elements, it will require little maintenance and can outlast a conventional home by decades. Because it is constructed to take advantage of the temperature-moderating effects of the earth’s immense thermal mass, it will stay warm in the winter and cool in the summer without demanding significant inputs from energy-consuming auxiliary heating and cooling systems. And because it is so incredibly well-sheltered by the warm embrace of the surrounding earth, an earth-sheltered home will be largely impervious to the ravages of natural disasters such as tornadoes, hurricanes, earthquakes, and wild fires, not to mention the predations of human intruders with bad intentions.
So while it may be a surprise to discover for some, earth-sheltered living is an exciting option that all who are willing to think outside the box in their search for a more efficient way of living should investigate fully before they proceed with their plans to construct their brand new homes.
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